如何在 MySQL 中判断中文字符？

原文出处： 温国兵

一 引子

在生产环境中，经常会有这样的场景：获得中文数据。那问题就来了，怎么才能匹配出中文字符呢？

本文提供两种方法。

二 演示

2.1 环境

mysql> SHOW VARIABLES LIKE "%version%";

+-------------------------+------------------------------+

| Variable_name | Value |

+-------------------------+------------------------------+

| protocol_version | 10 |

| version | 5.1.73 |

| version_comment | MySQL Community Server (GPL) |

| version_compile_machine | i386 |

| version_compile_os | apple-darwin10.3.0 |

+-------------------------+------------------------------+

5 rows in set (0.00 sec)

2.2 创建测试表和插入测试数据

mysql -S /tmp/mysql_5173.sock -uroot -proot

创建测试表和插入测试数据。

mysql> USE test;

Database changed

mysql> CREATE TABLE user

-> (name VARCHAR(20)

-> ) DEFAULT CHARSET = utf8 ENGINE = INNODB;

Query OK, 0 rows affected (0.10 sec)

mysql> SHOW TABLE STATUS LIKE 'user' G;

*************************** 1. row ***************************

Name: user

Engine: InnoDB

Version: 10

Row_format: Compact

Rows: 2

Avg_row_length: 8192

Data_length: 16384

Max_data_length: 0

Index_length: 0

Data_free: 0

Auto_increment: NULL

Create_time: 2015-01-16 18:01:36

Update_time: NULL

Check_time: NULL

Collation: utf8_general_ci

Checksum: NULL

Create_options:

Comment:

1 row in set (0.00 sec)

ERROR:

No query specified

mysql> INSERT INTO user VALUES('robin');

Query OK, 1 row affected (0.01 sec)

mysql> INSERT INTO user VALUES('温国兵');

Query OK, 1 row affected (0.00 sec)

三 实现

3.1 方法一 正则表达式

mysql> SELECT * FROM user G;

*************************** 1. row ***************************

name: robin

*************************** 2. row ***************************

name: 温国兵

2 rows in set (0.00 sec)

mysql> SELECT name,

-> CASE name REGEXP "[u0391-uFFE5]"

-> WHEN 1 THEN "不是中文字符"

-> ELSE "是中文字符"

-> END AS "判断是否是中文字符"

-> FROM user;

+-----------+-----------------------------+

| name | 判断是否是中文字符 |

+-----------+-----------------------------+

| robin | 不是中文字符 |

| 温国兵 | 是中文字符 |

+-----------+-----------------------------+

2 rows in set (0.00 sec)

mysql> SELECT name FROM user WHERE NOT (name REGEXP "[u0391-uFFE5]");

+-----------+

| name |

+-----------+

| 温国兵 |

+-----------+

1 row in set (0.00 sec)

3.2 方法二 length() 和 char_length()

mysql> SELECT name, length(name), char_length(name) FROM user;

+-----------+--------------+-------------------+

| name | length(name) | char_length(name) |

+-----------+--------------+-------------------+

| robin | 5 | 5 |

| 温国兵 | 20 | 9 |

+-----------+--------------+-------------------+

2 rows in set (0.00 sec)

mysql> SELECT name FROM user WHERE length(name) char_length(name);

+-----------+

| name |

+-----------+

| 温国兵 |

+-----------+

1 row in set (0.00 sec)